This invention relates to a horn actuator incorporated in an airbag unit which is mounted in a steering wheel of a motor vehicle, and more particularly to such an actuator in the form of a pressure or deflection sensitive switch which is provided with temperature compensation.
With the advent of the airbag, steering wheels became the most convenient location for mounting a driver's side airbag. Most often the airbag is mounted in the hub of the steering wheel. Since the steering wheel had also been a convenient location for other controls such as horn switches, the incorporation of airbag units within the steering wheel initially required the hardware for horn actuation to be moved from the center to small buttons on the steering wheel spokes. Since drivers are used to and feel more comfortable with the horn switch more centrally located on the steering wheel, technology has turned to attempting to put the horn actuation function back in the center of the steering wheel.
One approach is to incorporate some form of pressure or deflection sensitive switch in the airbag cover at the hub of the steering wheel which, when deflected, actuates the horn. Among the problems with this approach is that as the cover changes temperature, the force required to activate the horn changes. This change is due to the changes in stiffness of the plastic cover itself with temperature. The lack of consistency in the horn blowing function could frustrate the vehicle operator and in some cases might cause an accident if the operator fails to actuate the horn as quickly as required due to different force actuation requirements.